Ok so I've candled all my hen, duck & goose eggs at 7 days, the hen eggs were the easiest to do, getting 93-95% with 2 questionable ones - I think the 1 shell was too thick & the other was very dark brown in colour.

The duck eggs & goose egg were harder though, I found 5 definite fertile duck eggs but the others looked to sort of have air sacs & shadows, & the goose egg was similar but had a definite air sac. Should I leave these a little longer? X

Fair enough, I just didn't want to leave eggs in rotting & giving them the potential to explode or ruin others. It's in 1 of the large brines a cabinet incubators & it's my 1st attempt doing several species at once, & I've got hen, quail, duck & goose eggs in & have just got to candle the quail eggs in a few days & some more duck ones I've placed in today in a week. But so far fertility seems reasonable, & we know all of our current stock make birds are fertile apart from my orpington cock as his girls haven't laid yet